The invention relates to a process for acylating benzene, toluene and anisole in the presence of catalytic amounts of ferric chloride. The acylated compounds are particularly useful for the preparation of unsaturated compounds, particularly aromatic dienes, via the Grignard reaction.
Acylation reactions in which the acyl group is introduced by substitution into aliphatic and aromatic compounds are well known in the art. The use of Friedel-Crafts catalysts such as aluminum chloride, ferric chloride and ferric oxide in catalytic amounts, stoichiometric amounts or in excess of stoichiometric amounts for the reaction of aromatic compounds with acyl chlorides, anhydrides or esters is well known. Such acylation reactions are typically effected under reflux at ambient pressure conditions and are often accompanied by poor yields and/or conversions to the desired acylated product.
The acylated products, such as ketones, are desirable intermediates for preparing unsaturated hydrocarbons. A particularly attractive synthesis route for preparing such olefinically unsaturated hydrocarbons is through the Grignard reaction. By this reaction, the acylated compound is reacted with a Grignard reagent. The resulting Grignard reaction product is converted to an alcohol which is separated from its reaction mixture and subsequently dehydrated in the presence of an acid catalyst to form the olefinically unsaturated hydrocarbon.